In the construction industry, when workers are operating at heights that are more than a few feet off the ground it is often necessary for safety or legal purposes for the worker to secure himself rigidly to a structure through the use of a lanyard, belt or a fall arrest system. In some cases a secure structure to which a lanyard or similar device can be attached will be readily available to the worker. For example, in certain types of steel construction situations there are often structurally sound steel members (beams, girders, etc.) to which a worker can easily secure himself in order to prevent an accidental fall. However, there are many other construction situations where such structures are not readily available. For example, in high-rise apartment building, condominium and office tower construction, where walls and other structural members are primarily concrete, there are often no structural features present that offer a mechanism to which a worker can safely secure his lanyard or lifeline. As a result, others have proposed a variety of different anchors or similar devices that can be used for anchoring purposes.
One such type of anchor is characterized by a plunger having a flared distal end that is pulled to compress a coiled spring during installation. Upon release, the spring biases the plunger into engagement with the wall of a pre-drilled or existing hole within a concrete wall or column. The integrity of the anchor is limited to the mechanical and frictional engagement of the plunger with the interior surface of the walls of the hole. In most cases multiple holes must be drilled on a daily basis as workers move from location to location, and since the springs often cannot be relied upon to maintain an adequate anchoring if left overnight. The need to physically drill holes into concrete structures also increases the costs associated with installing the anchor and in some instances could potentially lead to a weakening of the concrete structure.
Others have proposed the use of safety straps that are attached to reinforcement bars disposed within the concrete with the ends of the straps extending out through the exterior surface of the wall or column. Such straps typically have D-rings sewn onto their terminal ends which a worker can use to attach a lanyard or lifeline. The difficulties associated with anchors of this type include not only their need to be inserted into the wall during the forming stage, but also their propensity to become worn or frayed through contact with the rough exterior of the concrete. Anchors of this type are sacrificial in nature and cannot be reused. If they become damaged or are no longer needed they are simply cut at the point that they extend through the concrete wall and then disposed of.
Still others have sought to utilize holes that extend through concrete walls and pillars that are left behind when the tie rods that hold the forms necessary to pour the walls are removed. Anchors have been developed to be received within these holes or passageways. Such anchors are generally of the expansion type that operate through the movement of an angular or wedge-shaped structure that causes an outward extension of the inner end of the anchor, driving it into frictional contact with the inside surface of the receiving hole. While such devices have been somewhat successful, they too rely upon the frictional engagement of the interior end of the anchor with the interior surface of the hole through the concrete. As a result, inconsistencies in the diameter of the hole through the concrete and the possibility that the surface of the concrete may crumble under load, particularly if the concrete is still green and has not yet fully cured, present the potential for slippage of the anchor.